Better informed than his wife about the nature of their ancestors, M. de Guermantes had a command of memories which gave his conversation the fine feel of an ancient mansion, lacking in real masterpieces but still full of authentic pictures, of middling interest and imposing, giving an overall impression of grandeur.
In that translation, by Mark Treharne, the sentence even has Powell's rhythm and structure, more so than the Moncrieff-Kilmartin translation, which renders the sentence thus:
Better informed than his wife as to what their ancestors had been, M. de Guermantes had at his command memories which gave to his conversation a fine air of an ancient mansion, lacking in real masterpieces but still full of pictures, authentic, indifferent, and majestic, which taken as a whole has an air of grandeur.Having no French, I can't comment on the accuracy of either version, but the Powell tone in particular seems to arise from the replacement of the string of descriptive adjectives--"authentic, indifferent, and majestic"--with the descriptive clause, "of middling interest and imposing." The word "middling," meanwhile, seems both more effective than "indifferent" and more Powellian, reminding us as it does that much of the stuff of the world is mediocre--yet so often proves to be of some unexpected interest anyway.
Powell was never shy about acknowledging his debt to Proust. I'm pretty much just playing late-night reading games here, but now I begin to wonder if Treharne is a Powell fan?
And, more important, if we're going to steal Proust's line for Dance, to whom should we attach it? Sir Gavin Walpole-Wilson, maybe?